Fistula formation devices and methods therefor

ABSTRACT

Described here are devices, systems, and methods for forming a fistula between two blood vessels. Generally, the systems may comprise a first catheter and a second catheter, which may comprise one or more fistula-forming elements. The first and second catheters may comprise one or more magnetic elements, which may be used to assist in bringing the first and catheters in closer proximity to facilitate fistula formation. In some variations, the magnetic elements may have magnetization patterns such that the flux generated by the magnetic elements is locally concentrated. In some instances, the system may comprise a magnetic control device, which may comprise a magnet, and may be used to increase or create an attractive force between the first and second catheters.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 61/785,509, filed on Mar. 14, 2013, and titled “FISTULA FORMULATIONDEVICES AND METHODS THEREFOR,” the content of which is herebyincorporated in its entirely.

FIELD

The current invention relates to devices and methods for forming afistula. The devices and methods may be used to form a fistula betweentwo blood vessels.

BACKGROUND

A fistula is generally a passageway formed between two internal organs.Forming a fistula between two blood vessels can have one or morebeneficial functions. For example, the formation of a fistula between anartery and a vein may provide access to the vasculature for hemodialysispatients. Specifically, forming a fistula between an artery and a veinallows blood to flow quickly between the vessels while bypassing thecapillaries. In other instances, a fistula may be formed between twoveins to form a veno-venous fistula. Such a veno-venous fistula may beused to help treat portal venous hypertension. Generally, fistulaformation requires surgical dissection of a target vein, and transectingand moving the vein for surgical anastomosis to the artery. It maytherefore be useful to find improved ways to form a fistula between twoblood vessels.

BRIEF SUMMARY

Described here are devices and systems for forming a fistula. In somevariations, the systems described here may comprise a first catheter anda second catheter. The first catheter may comprise one or morefistula-forming elements. Additionally or alternatively, the secondcatheter may comprise one or more fistula-forming elements. The firstand second catheters may comprise one or more magnetic elements, whichmay be used to move the first and second catheters in closer proximityto facilitate fistula formation. In some variations, the magneticelements may have magnetization patterns such that the magnetic fieldgenerated by the magnetic elements is locally concentrated. In someinstances, the system may comprise a magnetic control device, which maycomprise a magnet, and may be used to increase or create an attractiveforce between the first and second catheters.

In some variations of the systems described here, the system maycomprise a first catheter comprising a first magnetic element and asecond catheter comprising a second magnetic element, such that at leastone of the first and second catheters comprises a fistula-formingelement. The fistula-forming element may be any suitable structure, suchas an electrode. In some variations, the first magnetic element may beconfigured to produce a magnetic field that is stronger on a first sideof the first magnetic element than on a second side of the magneticelement. In some variations, the first magnetic element may comprise aplurality of regions each having a polarity. The plurality of regions ofthe first magnetic element may be configured such that the polarity ofeach region is rotated a first angle relative to the polarity of animmediately-preceding region in a proximal-to-distal direction. In someof these variations, the second magnetic element may comprise aplurality of regions each having a polarity. The plurality of regions ofthe second magnetic element may be configured such that the polarity ofeach region is rotated a second angle relative to the polarity of animmediately-preceding region in a proximal-to-distal direction. Thefirst angle may or may not be the same as the second angle. The firstand second angles may be any suitable angles (e.g., about 30 degrees,about 45 degrees, about 90 degrees). In some variations, the firstmagnetic element may have a plurality of regions such that the polarityof each region is rotated a first angle clockwise relative to animmediately-preceding region, and the second magnetic element may have aplurality of regions such that each region is rotated a first anglecounterclockwise relative to an immediately-preceding region.

In some variations, the systems may comprise a magnetic control device,which may comprise a housing having a contact surface for placementagainst the skin, a magnet, and a control element connected to themagnet and moveable relative to the housing such that the controlelement may move the magnet relative to contact surface. In somevariations, the magnet may comprise a magnetic array having amagnetization pattern. In some variations, the housing and/or controlelement may comprise one or more finger rings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustrative depiction of a variation of a system describedhere comprising a first catheter and a second catheter.

FIGS. 2A-2B, 3A-3B, and 4 are illustrative depictions of variations ofmagnetic arrays having magnetization patterns suitable for use with thecatheters described here.

FIGS. 5A-5B are illustrative depictions of a perspective view and across-sectional side view, respectively, of a variation of a magneticcontrol device as described here.

FIGS. 6A-6B, and 7-10 are illustrative depictions of variations ofmagnetic arrays having magnetization patterns suitable for use withmagnetic control devices described here.

FIGS. 11A-11C are illustrative depictions of a method of manipulatingone or more catheters using one or more externally placed magnets.

DETAILED DESCRIPTION OF THE INVENTION

Generally described here are systems, devices, and methods for forming afistula between blood vessels. The fistula may be, for example, anarteriovenous fistula between an artery and a vein, or a veno-venousfistula between two veins. Generally, to form a fistula between twoblood vessels, one or more catheters may be advanced in a minimallyinvasive fashion through the vasculature to a target fistula formationsite. Typically, a catheter may be placed in each of the two bloodvessels, such that a first catheter may be positioned in a first bloodvessel and a second catheter may be positioned in a second blood vessel.Accordingly, the systems described here may comprise a first catheterand a second catheter.

The first and second catheters may have one or more magnetic elements,which may be configured to aid in positioning and/or alignment of thecatheters. For example, in some instances the first catheter maycomprise one or more magnetic elements which may be attracted to one ormore magnetic elements of the second catheter, which may act to pull thefirst and second catheters toward each other. In some variations, themagnetic elements may have magnetization patterns such that the strengthof a magnetic field generated by the magnetic element is greater on oneside of the magnet than on an opposite side.

In some variations, the systems may also comprise a magnetic controldevice for applying a magnetic force to the first and second cathetersusing an external magnet positioned outside of the body. The magneticcontrol device may comprise a control element that may help to adjustthe position of the external magnet in a controlled manner. In someinstances, the external magnet may have a magnetization pattern suchthat the strength of the magnetic field generated by the external magnetis greater on one side of the magnet than on an opposite side. It shouldbe appreciated that each catheter may or may not have the sameconfiguration of elements, and that some catheters may be different fromand/or complementary to other catheters.

Devices

Catheters

As mentioned above, the systems described here typically comprise afirst catheter and a second catheter. Any suitable catheter or cathetersmay be used with the systems described here to form the fistulas usingthe methods described here. For example, in some variations the systemmay comprise one or more of the catheters described in U.S. patentapplication Ser. No. 13/298,169, filed on Nov. 16, 2011 and titled“DEVICES AND METHODS FOR FORMING A FISTULA,” the contents of which arehereby incorporated by reference in their entirety. Generally, eachcatheter may have a proximal end, a distal end, and an intermediateportion connecting the proximal and distal ends. The proximal end maycomprise one or more adaptors or handles, which may be utilized to helpaid in advancement, positioning, and/or control of the catheter withinthe vasculature, and may further be used to actuate one or morecomponents of the catheter and/or introduce one or more fluids orsubstances into and/or through the catheter. The catheter may compriseone or more elements that may aid in fistula formation. For example, oneor more portions (e.g., the distal end and/or the intermediate portion)of the catheter may comprise one or more elements, such as magnets, thatmay help to align the catheter with another catheter positioned in arelated blood vessel, and/or help to bring the catheters into closerapproximation, as will be described in more detail below. As thecatheters are brought in to closer approximation, the blood vesselswithin which the catheters are positioned may be brought into closerapproximation, which may aid in fistula formation. Additionally oralternatively, one or more portions (e.g., the distal end and/or anintermediate portion) of the catheter may comprise one or moremechanisms for forming a fistula.

The catheters may additionally comprise one or more lumens orpassageways extending at least partially along or through the catheter,and may be used to pass one or more guidewires, one or more drugs orfluids (e.g., contrast agents, perfusion fluids), combinations thereof,or the like at least partially along or through the catheter, but neednot comprise these lumens or passageways. The distal tip of the cathetermay be configured to aid in advancement of the catheter and/or to beatraumatic. In some variations, the tip may comprise one or more rapidexchange portions or other lumens for advancement of the catheter over aguidewire. In still other variations, the tip portion may have aguidewire attached to or otherwise integrally formed with the catheter.

Additionally, in some variations the catheters may further comprise oneor more external expandable elements (e.g., a balloon, expandable cage,mesh, or the like) that may help position a catheter within a bloodvessel, but need not comprise one or more external expandable elements.Additionally or alternatively, the one or more expandable elements mayaffect the flow of blood through one or more blood vessels (e.g., bytemporarily occluding blood flow through the blood vessel, dilating oneor more portions of a blood vessel, constricting one or more portions ofa blood vessel, or the like). In some instances, one or more expandableelements may act to temporarily anchor a portion of the catheterrelative to a blood vessel. In variations where the catheter comprisesone or more shape-changing elements, as will be described in more detailbelow, the use of an expandable element to temporarily anchor a portionof the catheter relative to a blood vessel may aid in altering the shapeof the catheter. It should be appreciated that the catheters describedhere may have any combination of the aforementioned elements.

FIG. 1 shows an illustrative variation of a catheter system that may beused to form a fistula between two vessels. As shown there, the systemmay comprise a first catheter (101) and a second catheter (103). Thefirst catheter (101) may comprise a catheter body (105), one or moremagnetic elements (107), and a fistula-forming element (109) which maybe activated to form a fistula. In some variations, the fistula-formingelement (109) may be advanced to project out of an opening (111) in thecatheter body (105). In some variations, the first catheter (101) maycomprise a housing (113), which may help protect other components of thefirst catheter (101) during fistula formation. For example, when thefistula-forming element (109) comprises an electrode configured toablate tissue, the housing (113) may comprise one or more insulatingmaterials which may shield or otherwise protect one or more componentsof the first catheter (101) from heat that may be generated by theelectrode during use.

As shown in FIG. 1, the second catheter (103) may also comprise acatheter body (115) and one or more magnetic elements (107). Invariations where the first catheter (101) comprises a fistula-formingelement (109) configured to project out the catheter body (105) of thefirst catheter (101), such as the variation depicted in FIG. 1, thecatheter body (115) of the second catheter (103) may comprise a recess(117) therein, which may be configured to receive the fistula-formingelement (109) as it passes through tissue. In some of these variations,the recess (117) may be coated by an insulating material (not shown),which may be configured to protect one or more components of the secondcatheter (103) from being damaged by the fistula-forming element (109)(e.g., the insulating material may shield one or more components of thesecond catheter (103) from heat that may be generated by thefistula-forming element (109)). While shown in FIG. 1 as having a recess(117), it should also be appreciated that in some variations the secondcatheter (103) may not comprise a recess (117). In some variations, thesecond catheter may comprise a fistula-forming element (not shown) inaddition to or instead of the fistula-forming element (109) of the firstcatheter (109), as will be described in detail below.

Fistula-Forming Elements

As mentioned above, the catheters described here may comprise one ormore elements for forming a fistula. The fistula-forming element maycomprise any element capable of forming a fistula between two vessels,such as those elements described in U.S. patent application Ser. No.13/298,169, which was previously incorporated by reference in itsentirety. For example, the fistula-forming element may comprise one ormore electrical mechanisms (e.g., electrodes or electrocauterymechanisms); one or more mechanical mechanisms (e.g., blades, lances,needles, or the like); one or more chemical devices (e.g.,enzyme-releasing devices); one or more cryogenic-cautery devices; one ormore laser ablation devices; and/or combinations thereof, and the like.A catheter may have any suitable number (e.g., zero, one, two, three, orfour or more) and combination of these fistula-forming elements. Thefistula-forming elements may be located in or on any suitable portion ofthe catheter (e.g., the distal end, an intermediate portion, orcombinations thereof). In variations where a catheter comprises two ormore fistula-forming elements, multiple fistula-forming elements may beused to create multiple fistulas, either simultaneously or sequentially.In other variations, multiple fistula-forming elements may interact toform a single fistula.

In variations where a system comprising multiple catheters is used tocreate a fistula between two blood vessels, each catheter may comprise afistula-forming element, but need not. Indeed, in some of thesevariations, only one catheter may comprise a fistula-forming element. Insome of these instances, the other catheter may still help align thecatheters and/or approximate the blood vessels, but may not directlycontribute to tissue removal. In variations where multiple catheterseach comprise a fistula-forming element, the catheters may havecomplimentary fistula-forming elements. For example, in variations wheretwo or more catheters comprise electrodes, one catheter may comprise anelectrode that acts as an active electrode, while another catheter maycomprise an electrode that acts as a passive or ground electrode.

In some variations of the catheters described here, a catheter maycomprise one or more electrodes for use in forming a fistula. When afistula-forming element comprises an electrode, it may be used to ablateor otherwise remove the tissue in contact with the electrode in order toform the fistula. If a fistula-forming element comprises an electrode,the electrode may be configured as described in U.S. patent applicationSer. No. 13/298,169, which was previously incorporated by reference inits entirety.

In the embodiment shown in FIG. 1, the fistula-forming element (109) ofthe first catheter (101) may comprise an electrode. The electrode may beselectively moved from a position in which the electrode is retained orotherwise held in the catheter body (105) to a position in which theelectrode extends away from the catheter body (105) (e.g., through theopening (111)), and the electrode may also be selectively moved back toa retracted/low-profile position (either the same or a differentposition as the previous retracted position) following ablation oftissue. This may allow the electrode to be maintained in a low-profileconfiguration during positioning of the catheter. In some variations,the electrode may be biased toward an extended position when nototherwise restrained by the catheter body (105).

Magnetic Elements

As mentioned above, the first and second catheters of the systemsdescribed here may comprise one or more magnetic elements. Generally,the magnetic elements may be configured to be attracted to one or moremagnetic fields (e.g., produced by one or more magnetic elements ofanother catheter, produced by one or more magnets positioned external tothe body). The magnetic element or elements may help to align orotherwise reposition the catheters when placed in the vasculature. Insome instances, a system may comprise first and second catheters eachhaving one or more magnetic elements, such that magnetic elements of thefirst catheter may be attracted to magnetic elements of the secondcatheter to bring the catheters in closer approximation. Additionally oralternatively, one or more external magnetic elements may be positionedoutside of the body, and may attract the one or more magnetic elementsof the first and/or second catheters to help reposition the first and/orsecond catheters, as will be described in more detail below. In otherinstances, one or more magnetic elements may help to ensure that one ormore catheters are in proper axial or rotational alignment relative toanother catheter or catheters, such as described in further detail inU.S. patent application Ser. No. 13/298,169, which was previouslyincorporated by reference in its entirety, which may facilitatealignment of one or more fistula-forming elements relative to a targetfistula-formation site.

When the catheters described here comprise a magnetic element, it shouldbe appreciated that the magnetic element may be configured to generate amagnetic field, but need not. For example, in some variations a cathetermay have a magnetic element formed from one or more ferromagneticmaterials configured to become temporarily magnetized when exposed to amagnetic field. In these variations, when the magnetic element is placedin a magnetic field (such as one produced by a magnetic element ofanother catheter), the temporary magnetization may provide an attractiveforce to the catheter to move or reposition the catheter. Examples ofsuitable ferromagnetic materials which may be temporarily, but are notlimited to, cobalt, gadolinium, iron, nickel, alloys of these metalswith or without other metals such as alnico, chemical compounds such asferrites, and/or a combination of any of these metals or their alloys.

In instances where the magnetic element is configured to generate amagnetic field, the magnetic element may comprise a permanent magnet oran electromagnet. When a magnetic element comprises a permanent magnet,the magnet may be made of any suitable material capable of generating amagnetic field. In some instances, the magnetic elements may bepermanent magnets made out of ferromagnetic materials. For example, insome variations, the magnetic elements may comprise one or morerare-earth magnets (e.g. samarium-cobalt magnets or neodymium magnets),and/or cobalt, gadolinium, iron, nickel, alloys of these metals with orwithout other metals such as alnico, chemical compounds such asferrites, and/or a combination of any of these metals or their alloys.When a magnetic element comprises an electromagnet, the electromagnetmay be selectively activated to produce a magnetic field. For example,when one or more catheters of the systems described here comprise one ormore electromagnets, the electromagnets may be activated before fistulaformation to bring the blood vessels within which the catheters arelocated in closer approximation; they may remain activated duringfistula formation to hold the vessels in closer approximation during thefistula-formation procedure; and then they may be deactivated after thefistula-formation procedure is complete. When a catheter comprisesmultiple electromagnet-based magnetic elements, these magnetic elementsmay be independently activated or may be activated as a group.

When the systems described here comprise a first catheter and a secondcatheter each comprising one or more magnetic elements, each cathetermay comprise any combination of permanent magnets, ferromagneticelements, or electromagnets. For example, in some variations, the firstcatheter may include only permanent magnets. In these variations, thesecond catheter may include only permanent magnets, only ferromagneticelements, only electromagnets, or a mix of some or all of theseelements. In other variations the first catheter may include onlyferromagnetic elements. Again, the second catheter may include onlypermanent magnets, only ferromagnetic elements, only electromagnets, ora mix of some or all of these elements. In still other variations, thefirst catheter may include a permanent magnets and ferromagneticelements. In these variations, the second catheter may include onlypermanent magnets, ferromagnetic elements, only electromagnets, or a mixof some or all of these elements.

When the catheters of the systems described here comprise one or moremagnetic elements, each catheter may comprise any number of individualmagnetic elements (e.g., one, two, three, four, five, six, seven, oreight or more, etc.). In variations where a catheter comprises aplurality of magnetic elements, these magnetic elements may be groupedinto one or more arrays. The magnetic elements or arrays may be locatedinside or outside of a catheter body or both. The magnetic elements orarrays may be positioned anywhere along the length of the catheter. Insome variations where the system comprises a first catheter having afistula-forming element (such as the first catheter (101) shown in FIG.1), the first catheter may comprise one or more magnetic elements orarrays proximal to a fistula-forming element. Additionally oralternatively, the first catheter may comprise one or more magneticelements or arrays distal to a fistula-forming element. In somevariations in which a system comprises a second catheter comprising afistula-forming element, the second catheter may comprise one or moremagnetic elements or arrays proximal to the fistula-forming element.Additionally or alternatively, when the second catheter comprises afistula-forming element, the second catheter may comprise one or moremagnetic elements or arrays distal to the fistula-forming element. Invariations where both the first and second catheters comprise one ormore magnetic elements or arrays, each magnetic element or array in thefirst catheter may be configured to align with one or more magneticelements or arrays in a second catheter. Each magnetic element may befixed in or on a catheter by any suitable method. For example, in somevariations one or more magnetic elements may be embedded in, adhered to,or friction-fit within a catheter.

Each magnetic element included in the catheters described here may haveany suitable size and shape. For example, each magnetic element may becylindrical, semi-cylindrical, tube-shaped, box-shaped, planar,spherical, or the like. Generally, the dimensions of the magneticelements may be constrained by size of the catheters carrying themagnetic elements, which in turn may be constrained by the anatomicaldimensions of the vessels through which the catheters described here maybe advanced. For example, if the catheter is to be advanced through ablood vessel having an internal diameter of about 3 mm, it may bedesirable to configure any magnetic element to have an outer diameter ofless than about 3 mm to reduce the risk of injury to vessel walls duringadvancement and manipulation of the catheter. Each magnetic element mayhave any suitable length (e.g., about 5 mm, about 10 mm, about 15 mm,about 20 mm, or the like), although it should be appreciated that insome instances longer magnets may limit the flexibility of the catheterto maneuver through tissue.

As mentioned above, when two catheters each comprise one or moremagnetic elements, the magnetic elements of the catheters may produce anattractive force between the catheters which may act to pull thecatheters into closer approximation. Once the first and second cathetershave been positioned, the attractive force may also act to maintain therelative positioning between the catheters. When the first and secondcatheters are placed in respective blood vessels, tissue positionedbetween the blood vessels may limit the ability of the first and secondcatheters to be brought toward each other. Accordingly, it may bedesirable to maximize the attractive force between the first and secondcatheters in order to help the first and second catheters to displacetissue between the blood vessels.

In some variations, in order to increase the attractive force betweentwo catheters, it may be desirable to focus the strength of a magneticfield generated by a magnetic element or array of magnetic elements. Insome instances, it may be desirable to focus the magnetic field producedby a magnetic element or array of magnetic elements such that thestrength of the magnetic field is greater on one side of the magnet thanthe strength of the magnetic field produced on an opposite side of themagnet. In other words, these locally-concentrated magnetic elements mayhave a magnetic flux distribution that is greater on one side of themagnetic element than on an opposite side of the magnetic element. Insome variations, one or more magnetic elements may be configured to havea substantially one-sided flux distribution. In these variations, theone or more magnetic elements may be configured such that the magneticelements produce a magnetic field on a first side of the magneticelements, but do not produce a significant magnetic field on a secondside of the magnetic elements. Accordingly, the flux distribution of themagnetic elements is limited to the first side of the magnetic elements,also known as a “one-sided flux” arrangement. While a one-sided fluxarrangement ideally produces no flux distribution on the second side ofthe magnetic elements, it should be appreciated that in practice aone-sided flux arrangement may produce negligible stray field on thesecond side of the magnetic elements (e.g., due to imperfections in themachining process or due to assembly of individually magnetic elements).When one or more magnetic elements are configured as a one-sided fluxarrangement, the strength of the magnetic field produced on the firstside of the magnetic elements may be twice the strength of a magneticfield produced by a standard magnet of a similar size, shape, andconstruction. In other variations, one or more magnetic elements may beconfigured to produce a magnetic field that is stronger on a first sideof the magnetic elements than it is on a second side of the magneticelements opposite the first side of the magnetic elements, but to alesser extent than a one-sided arrangement. For example, in somevariations, one or more magnetic elements may be configured to generatea magnetic field having a flux distribution on a first side of themagnetic elements that is about 1.5 times as much as the fluxdistribution on a second side of the magnetic elements, about 2 times asmuch as the flux distribution on a second side of the magnetic elements,about 3 times as much as the flux distribution on a second side of themagnetic elements, about 5 times as much as the flux distribution on asecond side of the magnetic elements, or the like.

Generally, to create a focused magnetic field as described immediatelyabove, a catheter may comprise one or more magnets having amagnetization pattern, such as a Halbach array, configured to generatethe desired magnetic field. Generally, the one or more magnets maycomprise an array of regions, where each region has a specific polarity.The direction of the polarity of each respective region may beselectively arranged to produce a pattern of magnetic polarities, whichmay alter overall magnetic field produced by the array. The array may beformed from one or multiple discrete magnets, as will be discussed inmore detail below.

FIG. 2A depicts one variation of a pair of magnetic arrays which may beconfigured to produce focused magnetic fields. Shown there are a firstmagnetic array (201) and a second magnetic array (203). The firstmagnetic array (201) may be configured to produce a magnetic field (notshown) that is stronger on a first side (i.e., the right side of thearray as depicted in FIG. 2A) of the array than on an opposite secondside (i.e., the left side of the array as depicted in FIG. 2A) of thearray. The second magnetic array (203) may be configured to produce amagnetic field (not shown) that is stronger on a first side (i.e., theleft side of the array as depicted in FIG. 2A) of the array than on anopposite second side (i.e., the right side of the array as depicted inFIG. 2A) of the array. When the first magnetic array (201) and secondmagnetic array (203) are positioned such that the first side of thefirst magnetic array (201) faces the first side of the second magneticarray (203) (such as shown in FIG. 2A), the magnetic field produced bythe first magnetic array (201) may attract the second magnetic array(203) toward the first magnetic array (201), while the magnetic fieldproduced by the second magnetic array (203) may in turn attract thefirst magnetic array (201) toward the second magnetic array (203).Because the fields produced by these magnetic arrays are localized, theattractive force provided by the arrays may be greater than thoseproduced by other similarly-sized magnets.

Generally, each of the magnetic arrays (201) and (203) are divided intoa plurality of regions (215), wherein each region has a magneticpolarity (represented by arrows (213)). The direction of the polaritiesof the regions (215) may change from one region to the next according toa magnetization pattern. For example, in the variation of the firstmagnetic array (201) depicted in FIG. 2A, the first magnetic array (201)may have a proximal end (205) and a distal end (209), and may have amagnetization pattern in which the polarity of each region is rotated 90degrees clockwise from the polarity of an immediately preceding regionwhen looking at the magnetization pattern in a proximal-to-distaldirection. Four regions (215 a), (215 b), (215 c), and (215 d) of thefirst magnetic array (201) having respective polarities (213 a), (213b), (213 c), and (213 d) are marked in FIG. 2A to help illustrate thispattern. As shown there, region (215 a) has a polarity (213 a) in afirst direction (e.g., to the left, as shown in FIG. 2A). Region (215b), the next region distal to region (215 a), has a polarity (213 b) ina direction that is rotated 90 degrees clockwise relative to thepolarity (213 a) of region (215 a) (e.g., toward the distal end (209) asdepicted in FIG. 2A). Similarly, region (215 c), the next region distalto region (215 b), has a polarity (213 c) in a direction that is rotated90 degrees clockwise relative to the polarity (213 b) of region (215 b)(e.g., toward the right as depicted in FIG. 2A). Finally, region (215d), the next region distal to region (215 c), has a polarity (213 d) ina direction that is rotated 90 degrees clockwise relative to thepolarity (213 c) of region (215 c) (e.g., toward the proximal end (205)as depicted in FIG. 2A). This pattern may be continued along the lengthof the first magnetic array (201). In the first magnetic array (201)shown in FIG. 2A, each region (215) may produce a magnetic field, butthe alternating polarities between adjacent regions may at leastpartially cancel out the magnetic field produced on the left side of themagnetic array (201) while augmenting the magnetic field produced on theright side of the magnetic array (201). It should be appreciated thatthe magnetic arrays described here having magnetization patterns mayhave any suitable number of regions (e.g., two or more regions, three ormore regions, four or more regions, five or more regions, ten or moreregions, or the like).

Similarly, in the variation of the second magnetic array (203) depictedin FIG. 2A, the second magnetic array (203) may have a proximal end(207) and a distal end (211), and may have a magnetization pattern inwhich the polarity of each region is rotated 90 degrees from thepolarity of an immediately preceding region when looking at themagnetization pattern in a proximal-to-distal direction. In the secondmagnetic array (203), the polarity of each region is rotated 90 degreescounter-clockwise from an immediately preceding region, as opposed toclockwise as in the first magnetic array (201). In these instances, eachregion (215) may again produce a magnetic field, but the alternatingpolarities between adjacent regions may at least partially cancel outthe magnetic field produced on the right side of the magnetic array(203) while augmenting the magnetic field produced on the left side ofthe magnetic array (203).

While the first and second magnetic arrays (201) and (203) are shown inFIG. 2A as having regions that each have a length equal to the width ofthe region, it should be appreciated that in some or all of the regionsof the magnetic arrays described here may have a length that isdifferent than the width of the region. For example, in some variationssome or all of the regions of a magnetic array may have lengths greaterthan their widths. In other variations, some or all of the regions of amagnetic array may have lengths shorter than their widths. Additionally,while each of the regions (215) of the first and second magnetic arrays(201) and (203) are shown in FIG. 2A as having the same length, itshould be appreciated that different regions may have different lengths.

The magnetic arrays described here having magnetization patterns may beformed from one or more magnets. For example, in some variations, amagnetic array may comprise a single magnet. In these variations, themagnet may be magnetized such that it has distinct regions withdiffering polarities. For example, in the some instances, the firstmagnetic array (201) and/or the second magnetic array (203) may beformed from a single magnet, such that each region of the magnet ismagnetized with a specific polarization. In other variations, a magneticarray may comprise a plurality of magnets. In these variations, eachregion of the array may be formed from a single magnet, or from multiplemagnets. For example, FIG. 2B shows a portion of a first magnetic array(221) and a second magnetic array (223). The first magnetic array (221)is shown as having a first region (225), a second region (227), and athird region (229), wherein each region has a polarity (represented byarrows (237)) that is rotated 90 degrees clockwise relative to that ofthe immediately preceding region when looking at the magnetizationpattern in a proximal-to-distal direction, similar to the magnetizationpattern of the first magnetic array (201) described above with respectto FIG. 2A. Similarly, the second magnetic array (223) is shown ashaving a first region (231), a second region (233), and a third region(235), wherein each region has a polarity that is rotated 90 degreescounter-clockwise relative to that of the immediately preceding regionwhen looking at the magnetization pattern in a proximal-to-distaldirection, similar to the magnetization pattern of the second magneticarray (203) described above with respect to FIG. 2A. As shown in FIG.2B, the first and third regions (225) and (229) of the first magneticarray (221) may each be formed from a single magnet, while the secondregion (227) may be formed from a plurality of individual magnets (e.g.,three magnets, which are labeled in FIG. 2B as (227 a), (227 b), and(227 c)). Similarly, the first and third regions (231) and (235) of thesecond magnetic array (223) may each be formed from a single magnet,while the second region (233) may be formed form a plurality ofindividual magnets (e.g., three magnets, which are labeled in FIG. 2B as(233 a), (233 b), and (233 c)). While the second regions (227) and (233)are shown as each comprising three magnets, an individual region may bemade up of any suitable number of magnets (e.g., one, two, three, orfour or more magnets).

In the magnetization patterns depicted in FIGS. 2A and 2B above, thepolarization of each region is shown as being either parallel orperpendicular to a longitudinal axis of the magnetic array. It should beappreciated, however, that in some variations, the polarities of theregions within a magnetization pattern may be positioned at any suitableangle. For example, in some variations, a magnetic array may comprise aplurality of regions where each region has a polarity that is rotated 90degrees relative to an immediately preceding region, and wherein thepolarity of each region is angled 45 degrees relative to thelongitudinal axis of the magnetic array. Additionally, while themagnetic arrays described above have magnetization patterns in whicheach region has a polarity that is rotated 90 degrees relative to thepolarity of an immediately preceding region, it should be appreciatedthat the angle between adjacent regions may be any suitable value. Forexample, in some variations, one or more magnetic arrays may have amagnetization pattern in which there is a 30 degree rotation between thepolarities of adjacent regions. FIG. 3A shows one such variation of apair of magnetic arrays. Shown there are a first magnetic array (301)having a proximal end (305) and a distal end (309) and a second magneticarray (303) having a proximal end (307) and a distal end (311). Each ofthe arrays may comprise a plurality of regions (315) each having apolarity (indicated by arrows (313)). The first magnetic array (301) mayhave a magnetization pattern in which the polarity of each region isrotated 30 degrees clockwise from the polarity of an immediatelypreceding region when looking at the magnetization pattern in aproximal-to-distal direction. Each region (315) of the first magneticarray (301) may produce a magnetic field, but the rotating polaritiesbetween adjacent regions may at least partially cancel out the magneticfield produced on the left side of the magnetic array (301) whileaugmenting the magnetic field produced on the right side of the magneticarray (301). Similarly, the second magnetic array (303) may have amagnetization pattern in which the polarity of each region is rotated 30degrees counter-clockwise from the polarity of an immediately precedingregion when looking at the magnetization pattern in a proximal-to-distaldirection. Each region (315) of the second magnetic array (303) mayproduce a magnetic field, but the rotating polarities between adjacentregions may at least partially cancel out the magnetic field produced onthe right side of the magnetic array (303) while augmenting the magneticfield produced on the left side of the magnetic array (303). Asmentioned above, the magnetic arrays may be formed from a single magnet(e.g., a single piece of material) which may have regions with differentof the magnet with different polarities as discussed above. In thesevariations, the polarity of the individual regions may be achieved bysubjecting the magnet to a complex magnetic field-pattern to set themagnetic pattern of the magnetic arrays.

For example, in other variations, one or more magnetic arrays may have amagnetization pattern in which there is a 15 degree rotation between thepolarities of adjacent regions. FIG. 3B shows one such variation of apair of magnetic arrays. Shown there are a first magnetic array (321)having a proximal end (325) and a distal end (329) and a second magneticarray (323) having a proximal end (327) and a distal end (331). Each ofthe arrays may comprise a plurality of regions (335) each having apolarity (indicated by arrows (333)). The first magnetic array (321) mayhave a magnetization pattern in which the polarity of each region isrotated 15 degrees clockwise from the polarity of an immediatelypreceding region when looking at the magnetization pattern in aproximal-to-distal direction. Each region (335) of the first magneticarray (321) may produce a magnetic field, but the rotating polaritiesbetween adjacent regions may at least partially cancel out the magneticfield produced on the left side of the magnetic array (321) whileaugmenting the magnetic field produced on the right side of the magneticarray (321). Similarly, the second magnetic array (323) may have amagnetization pattern in which the polarity of each region is rotated 15degrees counter-clockwise from the polarity of an immediately precedingregion when looking at the magnetization pattern in a proximal-to-distaldirection. Each region (335) of the second magnetic array (323) mayproduce a magnetic field, but the rotating polarities between adjacentregions may at least partially cancel out the magnetic field produced onthe right side of the magnetic array (323) while augmenting the magneticfield produced on the left side of the magnetic array (323).

In still other variations, one or more magnetic arrays may have amagnetization pattern in which there is a 45 degree rotation between thepolarities of adjacent regions. FIG. 4 shows one such variation of apair of magnetic arrays. Shown there are a first magnetic array (401)having a proximal end (405) and a distal end (409) and a second magneticarray (403) having a proximal end (407) and a distal end (411). Each ofthe arrays may comprise a plurality of regions (415) each having apolarity (indicated by arrows (413)). The first magnetic array (401) mayhave a magnetization pattern in which the polarity of each region isrotated 45 degrees clockwise from the polarity of an immediatelypreceding region when looking at the magnetization pattern in aproximal-to-distal direction. Each region (415) of the first magneticarray (401) may produce a magnetic field, but the rotating polaritiesbetween adjacent regions may at least partially cancel out the magneticfield produced on the left side of the magnetic array (401) whileaugmenting the magnetic field produced on the right side of the magneticarray (401). Similarly, the second magnetic array (403) may have amagnetization pattern in which the polarity of each region is rotated 45degrees counter-clockwise from the polarity of an immediately precedingregion when looking at the magnetization pattern in a proximal-to-distaldirection. Each region (415) of the second magnetic array (403) mayproduce a magnetic field, but the rotating polarities between adjacentregions may at least partially cancel out the magnetic field produced onthe right side of the magnetic array (403) while augmenting the magneticfield produced on the left side of the magnetic array (403). Asmentioned above, the magnetic arrays shown in FIG. 4 may be each beformed from a single magnet or from a plurality of individual magneticelements.

The ability to generate locally concentrated magnetic fields may allowthe catheters described here to increase the attractive force betweenthe catheters when the size of the catheters (and the magnetic elementsthereof) is otherwise constrained. Because the magnetic elements of thecatheters described may be advanced into the body, the patient's anatomymay place constraints on the dimensions of the catheters and themagnetic elements, such as discussed. Accordingly, a magnetic arraywhich generates a local magnetic field may help to maximize theattractive force between two catheters, which may allow the catheters toovercome additional compliance and/or resistance (e.g., by tissuebetween the vessels) to help bring the catheters into apposition.

It should be appreciated that although the magnetic arrays discussedabove with respect to FIGS. 2A-2B, 3A-3B, and 4 have been described aspairs, a catheter system may utilize any combination of magnetic arraysas described here. For example, when the systems described here comprisea first catheter and a second catheter, either the first and/or secondcatheter may have one or more magnetic elements that produce alocally-concentrated magnetic field. For example, in some variations, afirst catheter of a system may comprise one or more magnetic elementsthat produce a locally-concentrated magnetic field. The first cathetermay include any of the magnetic arrays discussed above with respect toFIGS. 2A-2B, 3A-3B, and 4. The second catheter may also comprise one ormore magnetic elements that produce a locally-concentrated magneticfield, but need not. In variations where each of the first and secondcatheters include one or more magnetic elements that produce alocally-concentrated magnetic field, the catheters may comprise anycombination of the magnetic arrays described above with respect to FIGS.2A-2B, 3A-3B, and 4. For example, in some variations, the first cathetermay comprise a first magnetic array having a magnetization patternhaving a first angle between the polarities of adjacent regions, and thesecond catheter may comprise a second magnetic array having a secondangle between the polarities of adjacent regions. In some variations,the first angle of the first magnetic array may be a clockwise rotationbetween adjacent regions in a proximal-to-distal direction, while thesecond angle of the second magnetic array may be a counter-clockwiserotation between adjacent regions in a proximal-to-distal direction. Inother variations, both the first angle of the first magnetic array andthe second angle of the second magnetic array may be a clockwiserotation (or both may be a counter-clockwise rotation) between adjacentregions in a proximal-to-distal direction. The first angle and secondangle may be any suitable value, such as described in more detail above,and the first angle may be the same as or different than the secondangle.

Magnetic Control Device

In another embodiment, the systems described may comprise a magneticcontrol device. This magnetic control device may be positionedexternally to the body, and may provide one or more magnetic forces toone or more catheters positioned in the body. Generally, the magneticcontrol device may comprise a magnet configured to increase theattractive force between two catheters to help bring the catheterstoward each other.

FIGS. 5A and 5B show one embodiment of a magnetic control device asdescribed here. FIGS. 5A and 5B depict a perspective view and across-sectional perspective view, respectively, of the magnetic controldevice (501). As shown there, the magnetic control device (501) maycomprise a housing (503) having a distal contact surface (505), a magnet(507) moveable relative to the housing (503), and a control element(509) for manipulating the magnet (507). In some variations, themagnetic control device (501) may comprise a spring (521) or otherstructure configured to bias the magnet (507) toward a specificposition, as will be described in more detail below, but need not.

Generally, the magnet (507) of the magnetic control device (501) may beat least partially housed within the housing (503). The magnet (507) maybe moveable relative to the housing (503) (as will be described below),and may be configured to increase the attractive force between twocatheters that may be positioned in the body when the magnet (507) ispositioned near the catheters. Because the magnet (507) is configured tobe positioned external to the body, the magnet (507) may not be subjectto the same size constraints as the magnetic elements of the cathetersdescribed here.

The magnet (507) of the magnetic control device may include anarrangement of one or more individual magnets, which may be configuredto generate any suitable magnetic field. For example, FIGS. 6A-6B and7-10 illustrate variations of magnetic arrangements that may be suitablefor use with the magnetic control devices described here. FIG. 6A showsone variation in which a magnetic arrangement (607) may comprise a firstmagnetic element (609) positioned on a first side of a centerline (610),and a second magnetic element (611) positioned on the other side of thecenterline (610) and attached to the first magnetic element (609) suchthat the polarity (indicated by arrow (615)) of the first magneticelement (609) is opposite the polarity (indicated by arrow (617)) of thesecond magnetic element (611). The magnetic arrangement (607) may createa magnetic field (represented in FIG. 6A by field lines (619)), whichmay be configured to pull magnetic elements toward the centerline (610)of the magnetic arrangement (607).

For example, when a first catheter (601) and a second catheter (603) arepositioned in the body beneath the surface of the skin (represented inFIG. 6A as line (613)), the magnetic arrangement (607) may be positionednear the skin (613) such that the centerline (610) passes between thefirst catheter (601) and the second catheter (603). For example, whenthe first and second catheters are positioned in a plane substantiallyparallel to the skin (613), this may include positioning the magneticarrangement (607) such that the centerline (610) is substantiallyperpendicular to the skin (613). The first and second catheters (601)and (603) may each comprise one or more magnetic elements (not shown),which may be responsive to the magnetic field produced by the magneticarrangement (607). For example, in some variations the first and secondcatheters (601) and (603) include magnetic elements each having apolarity (indicated in FIG. 6A by arrows (616)) such that the magneticfield produced by the magnetic arrangement (607) may pull each of thefirst and second catheters (601) and (603) toward the centerline (610).Since the centerline is positioned between the first and secondcatheters, this may move the catheters toward each other to bring themin closer approximation.

Each of the first magnetic element (609) and the second magnetic element(611) may be formed from one or more individual magnets. For example, inthe variation of the magnetic arrangement (607) depicted in FIG. 6A, thefirst magnetic element (609) may be formed from a single magnet and thesecond magnetic element (611) may be formed from a single magnet. Inother variations, one or more of the magnetic elements may be formedfrom multiple individual magnets. For example, FIG. 6B depicts avariation of the magnetic array (607) of FIG. 2A, except that the firstmagnetic element (609) is formed from three individual magnets (labeledas (609 a), (609 b), and (609 c)) and the second magnetic element (611)is formed from three individual magnets (labeled as (611 a), (611 b),(611 c)). While each of the first and second magnetic elements is shownin FIG. 2B as being formed from three individual magnets, it should beappreciated that the magnetic elements may be formed from any suitablenumber of individual magnets (e.g., one, two, three, or four or moremagnets).

The magnetic array (607) may have any suitable dimensions. For example,the magnet array may have any suitable height, such as for example,between about 5 mm and about 25 mm, between about 10 mm and about 20 mm,or the like. Similarly, the array may have any suitable width, such as,for example, between about 5 mm and 35 mm, between about 8 mm and 28 mm,between about 10 mm and about 20 mm, or the like. The array may furtherhave any suitable depth, such as, for example, between about 5 mm andabout 40 mm, about 8 mm and about 28 mm, between about 10 mm and about20 mm, or the like. While the variation of magnetic array (607) shown inFIG. 6A has a height that is greater than its width, in some instancesthe width of magnet (607) may be greater than or equal its height.

In other embodiments, the magnetic array may have a magnetizationpattern which may generate a locally-concentrated magnetic field on oneside of the array. For example, FIG. 7 illustrates a magnetic array(707) comprising a centerline (710) and a three-region magnetizationpattern. Specifically, the magnetic array (707) may comprise threeregions (707 a), (707 b), (707 c), where the polarity (indicated in FIG.7 by arrows (708)) of each region in magnetic array (707) is rotatedninety degrees relative to adjacent regions. In the variation of themagnetic array (707) shown in FIG. 7, the polarity of the left region(707 a) may be in a first direction (e.g., parallel to the centerline(710)), the polarity of the middle region (707 b) may be rotated ninetydegrees clockwise from that of the left region (707 a) (e.g., in adirection perpendicular to the centerline (710)), and the polarity ofthe right region (707 c) may be rotated ninety degrees clockwise fromthat of the middle region (707 b) (e.g., in a direction parallel to thecenterline (710), but opposite the first direction). In thesevariations, the magnetic array (707) may produce a stronger magneticfield on one side of the magnetic array (707) (e.g., the bottom side ofthe array (707) as shown in FIG. 7) than on an opposite side of thearray (707) (e.g., the top side of the array (707) as shown in FIG. 7).The magnetic field created by the magnetic array (707) may be configuredto pull magnetic elements toward the centerline (710) of the magneticarray (707).

For example, when a first catheter (701) and a second catheter (703) arepositioned in the body beneath the surface of the skin (represented inFIG. 7 as line (713)), the magnetic arrangement may be positioned nearthe skin (713) such that the centerline (710) passes between the firstcatheter (701) and the second catheter (703). For example, when thefirst and second catheters are positioned in a plane substantiallyparallel to the skin (713), this may include positioning the magneticarrangement (707) such that the centerline is substantiallyperpendicular to the skin (713). The first and second catheters (701)and (703) may each comprise one or more magnetic elements (not shown),which may be responsive to the magnetic field produced by the magneticarrangement (707). For example, in some variations the first and secondcatheters (701) and (703) include magnetic elements each having apolarity (indicated in FIG. 7 by arrows (716)) such that the magneticfield produced by the magnetic arrangement (707) may pull each of thefirst and second catheters (701) and (703) toward the centerline (710).Since the centerline is positioned between the first and secondcatheters, this may move the catheters toward each other to bring themin closer approximation. The magnetic array (707) may have any suitabledimensions, such as those described above with respect to the magneticarray (607) of FIGS. 6A and 6B.

In the magnetic array (707) shown in FIG. 7, the magnetic array may beformed from one or more magnets. In some instances, the magnetic array(707) may be formed from a single magnet such that the regions (707 a),(707 b), (707 c) are portions of the same magnet having differentpolarities. In some variations, one or more of the regions (707 a), (707b), (707 c) may be formed by one or more separate magnets. In some ofthese variations, each of the regions is formed from one or moreseparate magnets. When a specific region is formed from one or moreseparate magnets, it should be appreciated that the region may be formedfrom a single magnet, or may be formed from a plurality of magnets, suchas described in more detail above. Additionally, while only threeregions are shown in the magnetic array (707), the magnetic array (707)may include any number of regions, wherein each region has a polaritythat is rotated 90 degrees clockwise relative to a polarity of theadjacent region to its left.

While the polarities in adjacent regions of the magnetic array (707) arerotated by 90 degrees, it should be appreciated that the magnetic arraysdescribed here may have magnetization patterns in which adjacent regionshave polarizations that are rotated any suitable angle (e.g., about 15degrees, about 30 degrees, about 45 degrees, about 60 degrees or thelike). For example, FIG. 8 shows one variation of a magnetic array (807)comprising five regions (807 a), (807 b), (807 c), (807 d), (807 e),wherein each region is rotated forty-five degrees clockwise relative tothe region on its left (when viewed from the orientation shown in FIG.8). In these variations, the magnetic array (807) may produce a strongermagnetic field on one side of the magnetic array (807) (e.g., the bottomside of the array (807) as shown in FIG. 8) than on an opposite side ofthe array (807) (e.g., the top side of the array (807) as shown in FIG.8). The magnetic field created by the magnetic array (807) may beconfigured to pull magnetic elements toward a centerline (810) of themagnetic array (807).

In instances when the two catheters positioned in the body lie in aplane that is substantially perpendicular to the surface of the skin, itmay be difficult to position an external magnet such that a centerlineof the magnet passes between the catheters. Accordingly, some of themagnets suitable for use with the magnetic control devices describedhere may be configured to bring the magnets in closer approximation whenthe catheters are aligned substantially perpendicular to a skin surface.For example, FIG. 9 shows a magnet (907) comprising a single polarity(indicated in FIG. 9 by arrows (915)), which may be configured toincrease the attractive force between a first catheter (901) and asecond catheter (903) that are positioned in a plane (910) that issubstantially perpendicular to the skin surface (913). In thesevariations, the magnet (907) may be positioned near the skin surface(913) such that the direction of the polarity (915) of the magnet (907)is aligned with the plane (910) of the first and second catheters. Inthese instances, the magnet (907) may generate a magnetic field that mayrepulse the first and second catheters. Since the first catheter (901)is positioned closer to the magnet (907) than the second catheter (903),the force applied by the magnet (907) to the first catheter may begreater than the force applied by the magnet to the second catheter,which may cause the first catheter to move toward the second catheter.In other instances, the magnet (907) may be configured to attract boththe first (901) and second catheter (903) toward the skin. Since thefirst catheter (901) is positioned closer to the skin, the tissue aroundthe skin may provide greater resistance to movement toward than magnetthan may be felt by the second catheter (903), which may draw the secondcatheter (903) toward the first catheter (901).

FIG. 10 illustrates another variation of a magnetic array (1007)configured to increase the attractive force between two cathetersaligned substantially perpendicular to a skin surface. As shown there,the magnetic array (1007) may comprise a magnetization patterncomprising three regions (1007 a), (1007 b), (1007 c), where thepolarity of each region in magnetic array (1007) is rotated ninetydegrees clockwise relative to the region on its left (when viewed fromthe orientation shown in FIG. 10). That is, the first region (1007 a)may have a polarity in a first direction (e.g., to the left in theorientation shown in FIG. 10), the second region (1007 b) may have apolarity that is rotated ninety degrees clockwise from the polarity ofthe first region (1007 a) (e.g., toward the top of the magnet (1007) inthe orientation shown in FIG. 10), and the third region (1007 c) mayhave a polarity that is rotated ninety degrees from the polarity of thesecond region (1007 b) (e.g., toward the right in the orientation shownin FIG. 10). In these variations, the rotating polarities of the regionsmay augment the magnetic field provided by a first side of the magneticarray (1007) (e.g., the bottom side in the orientation shown in FIG.10), which may be configured to increase the attractive force between afirst catheter (1001) and a second catheter (1003) that are positionedin a plane (1010) that is substantially perpendicular a skin surface(1013). In these variations, the magnet (1007) may be positioned nearthe skin (1013) such that the direction of the polarity of the secondregion (1007 b) is aligned with the plane (1010) of the first and secondcatheters. In these instances, the magnetic array (1007) may generate amagnetic field that may repulse the first and second catheters. Sincethe first catheter (1001) is positioned closer to the magnetic array(1007) than the second catheter (1003), the force applied by themagnetic array (1007) to the first catheter may be greater than theforce applied by the magnet to the second catheter, which may cause thefirst catheter to move toward the second catheter. In other variations,the magnetic array (1007) may be configured attract both the first(1001) and second (1003) catheters toward the skin of the patient, whichmay draw the second catheter (1003) toward the first catheter (1001) asdiscussed above with respect to the magnetic array (907) of FIG. 9. Theindividual regions of the magnetic array (1007) may be formed from oneor more individual magnets, such as described in more detail above.

As with the magnetic arrays discussed above, the magnetic arrays (907)and (1007) shown in FIGS. 9 and 10 respectively may have any suitabledimensions, and specifically may have any suitable height (e.g., betweenabout 5 mm and about 160 mm, between about 10 mm and about 150 mm,between about 20 mm and about 140 mm, between about 40 mm and about 120mm, between about 75 mm and about 85 mm, etc.), width (e.g., betweenabout 5 mm and about 50 mm, between about 10 mm and about 40 mm, betweenabout 18 mm and about 25 mm), and depth (e.g., between about 5 mm andabout 50 mm, between about 10 mm and about 40 mm, between about 18 mmand about 25 mm) While the variation of magnet (907) shown in FIG. 9 hasa height that is greater than its width, in some instances the width ofmagnet (907) may be greater than its height.

Returning to FIGS. 5A and 5B, the magnetic control device (501) maycomprise, in addition to the magnet (507), a housing (503) having acontact surface (505) a distal end of the housing that is configured tobe placed against the skin. The housing (503) may at least partiallyhouse the magnet (507), and the magnet (507) may be moveable relative tothe contact surface (505) of the housing to adjust the distance betweenthe magnet (507) and the contact surface (505). In use, the contactsurface (505) may be placed against a skin surface, and may act as astop which may limit movement of one or more catheters or tissuerelative to the magnet (507), as will be described in more detail below.The contact surface (505) may be formed from one or more rigid materials(e.g., a hard plastic or the like) or may be formed from one or moreflexible materials.

As mentioned above, the magnetic control device (501) may comprise acontrol element (509) configured to selectively move the magnet (507)relative to the housing (503) and the contact surface (505).Specifically, the magnet (507) may be fixed to the control element (509)(e.g., via one or more adhesives, bonding, welding or the like), and thecontrol element (509) may comprise a slider that is slidably connectedto the housing (503). The control element (509) may be advanced towardthe contact surface (505) to move the magnet (507) toward the contactsurface (505), and may be withdrawn away from the contact surface (505)to move the magnet (507) away from the contact surface (505). It shouldbe appreciated that while shown in FIGS. 5A and 5B as comprising aslider, the control element (509) may be any element or combination ofelements capable of moving the magnet (507) relative to the contactsurface (505), such as, for example, one or more knobs, triggers,cranks, levers, or the like. For instance, in one variation the controlelement may have a stapler-like configuration or a squeeze grip havingtwo members connected by a pivot joint. When an operator compresses thestapler-like configuration or squeeze grip by pressing the memberstoward each other, the magnet may be moved closer to the contactsurface. It should also be appreciated that in some embodiments, themagnet may be fixed relative to the contact surface of the magneticcontrol device.

In some variations, the magnetic control device (501) may comprise aspring (521) configured to bias the control element (509) away from thecontact surface (505). In these variations, a user may apply a force tothe control element (509) to overcome the bias provided by the spring(521) and advance the control element (509) and magnet (507) toward thecontact surface (505). When the force is released, the spring (521) mayreturn the control element (509) and magnet (507) to their originalpositions. Additionally or alternatively, the magnetic control device(501) may comprise one or more mechanisms configured to temporarilymaintain a position of the control element (509). For example, in somevariations the housing may comprise a series of teeth (not shown) whichmay be configured to allow one-way movement of the control element (509)relative to the teeth. In this variation, the teeth may engage thecontrol element (509) and/or the magnet (507) such that the controlelement (509) may move incrementally toward the contact surface (505),but may be prevented from moving away from the contact surface (505).Each incremental advancement may create an audible sound as the controlelement (509) and/or magnet (507) advances beyond each individual tooth,which may provide feedback to the user. The teeth may also be moveableto release the engagement between the teeth and the control element(509) and/or magnet (507), which may allow for retraction of the controlelement (509) and magnet (507) relative to the contact surface (505). Invariations where the magnetic control device (501) comprises a spring(521) as shown in FIGS. 5A and 5B, the spring (521) may return thecontrol element (509) and magnet (507) to their original positions whenthe teeth are disengaged from the control element (509) and/or magnet(507).

The housing and/or control element may have one or more grips or fingerrings configured to help allow a user to grab or hold the housing and/orcontrol elements, which may allow for an intuitive and ergonomic userinterface, and in some instances may allow the magnetic control device(501) to be manipulated with a single hand. For example, in theembodiment shown in FIGS. 5A and 5B, the housing (503) may comprise twofinger rings (513), and the control element (509) may comprise a fingerring (519) such that the finger rings may allow a user to grip themagnetic control device (501) in a syringe-like fashion. For example, auser may place one or more fingers in one or more of the finger rings(513) of the housing (503) and may place a thumb in the finger ring(519) of the control element (509), and may “squeeze” the finger ring(519) of the control element (509) toward the finger rings (513) of thehousing (503) to advance the control element (509) (and with it, themagnet (507)) toward the contact surface (505). While the housing (503)is shown in FIGS. 5A and 5B as having two finger rings, it should beappreciated that the housing need not have any finger rings (519), mayhave one finger ring, or may have three or more finger rings.

In some variations, the magnetic control device may comprise one or moreelements configured to releasably secure the magnetic control device tothe body. For example, in some variations the magnetic control devicemay comprise one or more straps (e.g., an elastic strap or the like)which may be connected to the housing, such that the strap may bepositioned around a limb (e.g., an arm) of a patient to temporarilyconnect the magnetic control device to the limb, which may allow themagnetic control device to remain in place without needing to be held bya user.

Systems

Also described here are systems for forming a fistula between two bloodvessels. Generally, the systems may comprise a first catheter, which maycomprise one or more fistula-forming elements and one or more magneticelements. The first catheter may comprise any one or more of any of thefistula-forming elements or combination of fistula-forming elements asdescribed in more detail above and in U.S. patent application Ser. No.13/298,169, which was previously incorporated by reference in itsentirety. The first catheter may comprise one or more magnetic elements,which may be any of the magnetic elements described in more detailabove. In some variations, the magnetic element may be a permanentmagnet or electromagnet generating a locally concentrated magnetic flux,or it may be a ferromagnetic material which may be temporarilymagnetized in the presence of a magnetic field. The first catheter maycomprise any suitable catheter body and may comprise one or more otherelements, such as one or more shape-changing elements or balloons suchas described in more detail in U.S. patent application Ser. No.13/298,169, which was previously incorporated by reference in itsentirety.

The systems described here may also comprise a second catheter. In somevariations, the second catheter may comprise a fistula-forming elementand one or more magnetic elements, but need not. In variations where thesecond catheter does comprise a fistula-forming element, the secondcatheter may comprise any one or more of any of the fistula-formingelements or combination of fistula-forming elements as described in moredetail above and in U.S. patent application Ser. No. 13/298,169, whichwas previously incorporated by reference in its entirety. Thefistula-forming element of the second catheter may be the same as ordifferent from the fistula-forming element of the first catheter. Thesecond catheter may comprise one or more magnetic elements, which may beany of the magnetic elements described in more detail above. In somevariations, the magnetic element may be a permanent magnet orelectromagnet generating a locally concentrated magnetic flux, or it maybe a ferromagnetic material that may be temporarily magnetized in thepresence of a magnetic field. The first catheter may comprise anysuitable catheter body and may comprise one or more other elements, suchas one or more shape-changing elements or balloons such as described inmore detail in U.S. patent application Ser. No. 13/298,169, which waspreviously incorporated by reference in its entirety.

The systems described here may further comprise a magnetic controldevice, such as described in more detail above which can be used tocontrol one or more magnetic elements of the first and/or secondcatheters from a position external to the body. The magnetic controldevice may comprise any elements or combinations of elements asdescribed in more detail above.

Methods

Also described here are methods for creating a fistula between two bloodvessels. The two blood vessels may be two closely-associated bloodvessels, such as a vein and an artery, two veins, etc. Generally, inthese methods one or more fistula-forming elements may be activated tobore through, perforate, or otherwise create a passageway between thetwo blood vessels such that blood may flow directly between the twoadjoining blood vessels. When such a fistula is formed, hemostasis maybe created without the need for a separate device or structure (e.g., asuture, stent, shunt, or the like) connecting or joining the bloodvessels.

Generally, the methods described here comprise accessing a first bloodvessel with a first catheter, and advancing the first catheter to atarget location within a blood vessel. A second blood vessel may beaccessed with a second catheter, and the second catheter may be advancedto a target location within the second vessel. In some of these methods,a first catheter may be advanced into an artery, and a second catheteris advanced into a vein. In other methods, a first catheter may advancedinto a first vein and a second catheter is advanced into a second vein.In yet other methods, a first catheter may be advanced into a firstartery and a second catheter is advanced into a second artery. Thecatheters may be advanced in any suitable manner, as described in moredetail in U.S. patent application Ser. No. 13/298,169, which waspreviously incorporated by reference in its entirety, and any of thecatheters described in that application may be used.

Once the first and/or second catheters have been advanced into therespective blood vessels, the catheters may be adjusted to affect thepositioning of the catheters within the blood vessels and/or thepositioning of the blood vessels relative to each other. In variationswhere a first catheter has been advanced into a first blood vessel and asecond catheter has been advanced into a second blood vessel, the firstand second catheters may be adjusted to bring at least a portion of thefirst and second catheters toward each other, which may act to bring theblood vessels in closer approximation. Adjusting the catheters maycomprise using one or more magnetic alignment elements, shape-changingmembers, markers, or balloons or expandable members, as described inmore detail in U.S. patent application Ser. No. 13/298,169, which waspreviously incorporated by reference in its entirety.

In variations where the first and second catheters comprise one or moremagnetic elements, the magnetic elements may result in an attractiveforce between the first and second catheters, which may pull thecatheters toward each other. For example, the first and/or secondcatheters may comprise one or more magnetic elements having amagnetization pattern such as described in more detail above.Additionally or alternatively, a magnet may be positioned externally tothe body and may act to bring the first catheter closer to the secondcatheter. For example, FIGS. 11A-11C depict a method by which themagnetic control device (501) described above with respect to FIGS. 5Aand 5B may be used to bring a first catheter towards a second catheter.For example, a first catheter (1101) may be placed in a first bloodvessel (not shown) and a second catheter (1103) may be placed in asecond blood vessel (not shown), such as shown in FIG. 11A. The magneticcontrol device (501) may be positioned to place the contact surface(505) against the skin surface (1113) of a patient near the first andsecond catheters, such as shown in FIG. 11A. In variations in which themagnetic control device (501) comprises a securing element, the securingelement may be used to secure the magnetic control device (501) to thepatient.

The magnet (507) may be configured to generate a magnetic fieldconfigured to move the first catheter (1101) toward the second catheter(1103) laterally, relative to the magnet, such as described in moredetail above. Specifically, the magnet (507) may be advanced (e.g.,using a control element (509) as discussed above) toward the contactsurface (505) from a retracted position (as shown in FIG. 11A) to anextended position (as shown in FIG. 11B). As the magnet (507) approachesthe extended position, the distance between the magnet (507) and thefirst and second catheters may decrease. This in turn may increase themagnitude of the force that the magnet (507) applies to the first andsecond catheters. As the force applied to the first and second cathetersis increased, the first and second catheters may be urged together, asshown in FIG. 11B.

Once the first and second catheters (1101) and (1103) have moved intocloser proximity, the magnet (507) can be moved away from contactsurface (505) (e.g., by retracting a control element (509), allowing thespring-bias provided by spring (521) to retract the control element(509), etc.) to move the magnet (507) away from the catheters (1101) and(1103), such as shown in FIG. 11C. When the magnet (507) applies anattractive force to the first and/or second catheters, movement of themagnet (507) away from the skin surface (1113) may pull the first and/orsecond catheters toward skin surface (1113). In these instances, thecontact surface (505) may act as a stop to push against the skin surface(1113) and limit tissue movement towards housing (503) as the magnet(507) is retracted (which may in turn reduce the likelihood that thefirst and/or second catheters may damage tissue by being pulled towardthe skin surface (1113). With the magnet (507) withdrawn, the magneticcontrol device (501) may be removed from its position relative to theskin surface (1113). The magnetic control device (501) may be removedbefore, during, or after fistula formation.

Once the catheter or catheters have been positioned and adjusted, one ormore fistula-forming elements may be used to create a fistula betweenthe two blood vessels. For example, in some variations, one of the firstand second catheters comprises a fistula-forming element (e.g., anelectrode, a cutting blade, or the like), while the other catheter doesnot comprise a fistula-forming element. In other variations, bothcatheters comprise a fistula-forming element. In some of thesevariations, the fistula-forming elements of the first and secondcatheters act to form different fistulas. In other variations, thefistula-forming elements of the first and second catheters interact toform the same fistula. For example, in some variations the first andsecond catheters each comprise at least one electrode. Any of themethods for using fistula-forming elements to create one or morefistulas described in U.S. patent application Ser. No. 13/298,169, whichwas previously incorporated by reference in its entirety, may be used.Additionally, one or more balloons may be used to modify a fistula afterthe fistula has been formed, to affect the blood flow relative to thefistula, or to determine that the fistula has been properly formed, asdescribed in more detail in U.S. patent application Ser. No. 13/298,169,which was previously incorporated by reference in its entirety.

We claim:
 1. A system for creating a fistula between two vessels,comprising: a first catheter comprising a first magnetic elementconfigured to be received within a first vessel; a second cathetercomprising a second magnetic element configured to be received in asecond vessel; and a device for applying a magnetic field to the firstand second magnetic elements, wherein: the magnetic field is configuredto move the first catheter laterally toward the second catheter, atleast one of the first and second catheters comprises a fistula-formingelement, the first magnetic element is configured to produce a magneticfield that is stronger on a first side of the first magnetic elementthan on a second side of the first magnetic element, and the firstmagnetic element comprises a plurality of regions each having apolarity, and wherein the plurality of regions of the first magneticelement is configured such that the polarity of each region is rotated afirst angle relative to the polarity of an immediately-preceding regionin a proximal-to-distal direction of the first magnetic element.
 2. Thesystem of claim 1 wherein the fistula-forming element is an electrode.3. The system of claim 1 wherein the second magnetic element comprises aplurality of regions each having a polarity, and wherein the pluralityof regions of the second magnetic element is configured such that thepolarity of each region is rotated a second angle relative to thepolarity of an immediately-preceding region proximal-to-distaldirection.
 4. The system of claim 3 wherein the first angle is the sameas the second angle.
 5. The system of claim 3 wherein the first angle isabout 90 degrees.
 6. The system of claim 3 wherein the first angle isabout 45 degrees.
 7. The system of claim 3 wherein the first angle isabout 30 degrees.
 8. The system of claim 3 wherein the plurality ofregions of the first magnetic element is configured such that thepolarity of each region is rotated a first angle clockwise relative tothe polarity of an immediately-preceding region in a proximal-to-distaldirection, and wherein the plurality of regions of the second magneticelement is configured such that the polarity of each region is rotated asecond angle counter-clockwise relative to the polarity of animmediately-preceding region proximal to-distal direction.
 9. A systemfor forming a fistula between two vessels, comprising: a first cathetercomprising a first magnetic element; a second catheter comprising asecond magnetic element, wherein at least one of the first and secondcatheters comprises a fistula-forming element; and a device for applyinga magnetic field to the first and second magnetic elements, comprising amagnet inside a housing, wherein the magnet is moveable within thehousing, and wherein the magnet is configured to generate a magneticfield that, when applied simultaneously to the first and second magneticelements, is capable of increasing an attractive force between the firstand second magnetic elements; and wherein the magnetic field isconfigured to move the first catheter laterally toward the secondcatheter.
 10. The system of claim 9, wherein the fistula-forming elementcomprises an electrode.
 11. The system of claim 9, wherein the firstmagnetic element comprises a plurality of regions each having apolarity, and wherein the plurality of regions of the first magneticelement is configured such that the polarity of each region is rotated afirst angle relative to the polarity of an immediately-preceding regionin a proximal-to-distal direction.
 12. The system of claim 11, whereinthe second magnetic element comprises a plurality of regions each havinga polarity, and wherein the plurality of regions of the second magneticelement is configured such that the polarity of each region is rotated asecond angle relative to the polarity of an immediately-preceding regionproximal-to distal direction.
 13. A method of forming a fistula betweena first blood vessel and a second blood vessel of a patient comprising:advancing a first catheter into the first blood vessel, wherein thefirst catheter comprises a first magnetic element; advancing a secondcatheter into the second blood vessel, wherein the second cathetercomprises a second magnetic element, and wherein at least one of thefirst and second catheters comprises a fistula-forming element;positioning an external magnet external the patient, wherein the magnetproduces a magnetic field; increasing an attractive force between thefirst and second magnetic elements when applying the magnetic fieldsimultaneously to the first and second magnetic elements, wherein themagnetic field is configured to move the first catheter laterally towardthe second catheter; and forming a fistula with the fistula-formingelement.
 14. The method of claim 13 wherein the positioning the externalmagnet external to the body comprises positioning the external magnetusing a magnetic control device, wherein the magnetic device comprisesthe external magnet and a housing having a contact surface.
 15. Themethod of claim 14 further comprising positioning the contact surface ofthe housing in contact with a skin surface of the patient.
 16. Themethod of claim 14 further comprising moving the external magnet towardthe contact surface to increase a force applied by the magnetic field toat least one of the first and second catheters.
 17. The method of claim13 wherein the fistula-forming element is an electrode, and whereinforming the fistula with the fistula-forming element comprises ablatingtissue with the electrode.
 18. The method of claim 13 wherein the firstblood vessel is a vein and the second blood vessel is an artery.